Carburetor process for acetylene reactions



Patented June 1, 1949 2 472 035,

' CARBI IRETOR PROCESS FOR ACETYLENE I REACTIONS Hans Beller, Crawford, and Robert E. Christ and Fritz Wuerth, Elizabeth, N. J assignors to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application October-10, 1945,

Serial No. 521,622 a s cnhmi. (Cl. 260-468) 1 2 The present invention relates to a process for of a volatile, normally liquid, organic diluent in producing vinyl esters of carboxylic acids. any desired manner. It is preferable to intro- A process for producing vinyl esters of carduce into the acetylene the required amount of boxylic acids by reacting acetylene, at elevated vapors of a volatile, normally liquid, organic temperatures and preferably elevated pressures, 5 diluent-while the acetylene is at a relatively low with carboxylic acids in liquid phase and in the pressure and/or temperature, 1. e., conditions at presence of a small amount of a cadmium or zinc which it is non-explosiv and thereafter comsalt of a carboxylic acid as a, catalyst, has been press it to the pressure desired for the reaction described in United States Patent No. 2,066,075 and, if necessary, heat it to the reaction temto Reppe. perature. However, by employing slow acting While it is preferable to employ elevated temcompressors and cooling during compression, it is peratures and pressures in practicing the abovepossible to bring undiluted acetylene to a relamentioned process, and, in fact, such reaction tively high pressure with reasonable safety, and conditions arenecessary if a satisfactory rate the vapors of the volatile, normally liquid, orof reaction and yield are to be obtained, the inganic diluent may then be introduced into the herent instability of acetylene under such reaccompressed acetylene. While the particular tion conditions has heretofore introduced numet d of ntrodu ng t e d u nt p s to th merous difiiculties in practicing this process. In acetylene does not, per m a P f the order to render the acetylene reasonably safe unpr n nv n i n. d n m r us ns f r acder the preferred reaction conditions, it has been eompllshing, this introduction e e necessary to dilute it sufiiciently with inert gases, scri ed in our v -m nt eopendil'lg app such as nitrogen, hydrogen, carbon monoxide, Cation, d t y, e acetylene maybe methane 0r ethane in order to preclude x locontacted with the desired diluent, while the sions. A mixture of 2 volumes of acetylen with diluent is in liquid phase and is maintained at 1 volume of nitrogen, hydrogen or another of the such a temperature that the acetylene will take aforesaid gaseous diluents usually has been emup or become carbureted with a suflicient amount ployed. This dilution of the acetylene with inert f v pors f the diluent that it will be non-exgaseous diluents has resulted in a substantial inl p ive at t e reaction i i n to e p y crease in the over-all pressure which is required n practicing t e p e n invention, i Sh ld be and has materially lowered the rate of reaction r e in i d t a in r r t pr ude th P08- and yield at any given reaction conditions. In sibllity of explosion, not only should the ac tyaddition to these and th u d i b pr clene which is supplied to the reaction be diluted ess effects, it has substantially increased the size h the Vapors of a V l lly iq 0 of the plant and auxiliary equipment required for ni l nt but ny nr d etylene recarrying out the reactio moved from the reaction mixture should be simi- We have now found that this reaction ma be larly diluted so long as it is under an elevated carried out at relatively lower pressures and with P e t mp ur a relatively higher rate of reaction and yield The Volatile, norm y Organic C p d under any given reaction conditions if the acety- Which is empl to dilute 01 r urize he lene employed in th process i mi t acetylene may, in case the vinyl ester to be prosuificient amount of the vapors of a volatile, norduced is that of a volatile organl a i e the man liquid, organic d m m; t eliminate the vapors of the acid itself or a-volatile ester, which danger of explosion in the manner described in tllrll y be a Product O lihe reaction. if our copending application Serial No, 621,620 sired, thereof. In addition, practically any vola- When the acetylene is diluted in this manner tile organic compound which is inert under the with the vapors of a volatile, normally liquid, or- Conditions Of the r c n may be empl s ganic diluent, not only are the desired process e dill-lent Carbureting agentit e eflects of elimination of the dangers of explosion pounds o such se ay be i ed t e overcome and, at any given reaction conditions, lower aliphatic q i r o s, S ch as a ithe improvement in yield and rate of reaction ph llic 01 y l liph fi hydrocarbons, for obtained, but in addition, the capital cost of plant ple, hexan h p a ane, cyolohexane and necessary for practicing the process may be subothers, their isomers or mixtures thereof, for instantiallyreduced. stance, volatile petroleum fractions, also many In practicing the present invention, the acetyaromatic or naphthenic hydrocarbons, such as lene is saturated or carbureted with the vapors benzene, toluene, xylene and the like, and in addition, certain heterocyclic compounds. A wide variety of such compounds as ethers, esters, etc.,

with the reaction conditions to be used and also with the specific compound being employed as a diluent a suillcient amount of diluent or carburizing agent being employed to preclude the possibility of explosions. The limits of explosability or the degree of dilution which is necessary may be determined readily for any particular conditions by simple preliminary test. Thus, for instance, acetylene gas, together with a predetermined amount of diluent vapor may be enclosed in a pressure vessel under test pressure and heated to the test temperature and any possible explosion initiated by means of an electrically heated wire provided within the pressure vessel. The reaction may be carried out in the presence of an inert liquid diluent or solvent which may be the same as or diflerent from the diluent employed for the acetylene. As examples of suitable solvents may be mentioned aliphatic, aromatic or hydroaromatic hydrocarbons, such as benzene, petroleum fractions, toluene, xylene, cyclohexane, tetrahydronaphthalene. esters, for instance, the vinyl esters obtainable according to the present process, or such esters as methyl, ethyl, n-butyl, isobutyl or am] acetate or butyrate.

when the acetylene, diluted with a suflicient amount of vapors of a volatile, normally liquid, organic diluent to preclude the possibility of explosion, is admixed with a carboxylic acid in the presence of a small amount of a suitable catalyst, and the reaction mixture maintained at predetermined reaction conditions, the acetylenereadily reacts with the carboxylic acid to form vinyl esters. It appears that the probable course of reaction is in accordance with the following equation:

Zn 202E:

The process of the present invention is applicable to the production of vinyl esters of organic acids, as for example, sallcyclic acid or hydroxy naphthoic acid; and in addition, heterocyclic acids, such as pyridine and quinoline carboxylic acids, and hydroaromatic carboxylic acids, for example, hydrophthalic acid. Instead of pure acids, partially esterified acids or resins showing a high acid value, such as colophony, or mixtures of acids may be employed, as for example, the acids obtainable by saponiflcation of natural fats and fatty oils containing esters and all fatty acids or the mixtures of acids obtainable by the partial oxidation of selected petroleum fractions, for instance, paraflln wax, and the like.

The reaction is catalyzed by zinc and cadmium salts of organic acids, and suitable catalysts are such compounds as zinc acetate, zinc stearate, zinc benzoate or the corresponding cadmium salts. These salts may be added, as such, to the acid treated with acetylene or they may be prepared by dissolving the zinc or cadmium oxides in the acids to be employed. In practicing the present process, it is preferable to employ at least 7.5% of catalyst, calculated as ZnO or CdO with reference to the acid employed, and generally speaking, the quantity of the catalyst is between 0.5 and about 5%.

The vinyl esters produced in accordance with the present invention may be recovered in any suitable manner from the reaction mass, for instance, by extraction with suitable solvents or by distillation, under vacuum, if necessary. Various l polymerization inhibitors, such as hydroquinone,

acid and the different isomers of naphthoic acid,

also mixed aliphatic-aromatic acids, as for example, phenyl acetic acid, cinnamic acid, phenyl glycine and polybasic cyclic acids or their acid esters, such as phthalic acid and phthalic acid monoalkyl esters, for example, mono-ethyl, normal or naphthols, or amines may be added during the distillation or on subsequent storage of the vinyl esters. The vinyl esters obtained according to this invention may be polymerized by the usual methods.

The following examples will further illustrate how this invention may be carried out in practice, but the invention is not restricted to these examples: I

Example 1 Acetylene at a pressure of 4 pounds per square inch, free from moisture and other impurities, is passed through a bath of acetic acid maintained at 118 C. The acetylene is saturated with acetic acid and is then compressed to 45 pounds per square inch and then heated to a temperature of C. It is then introduced into the bottom of a tower filled with glacial acetic acid, held at a temperature of C. in which is dissolved approximately 4% by weight of zinc acetate. The acetylene reacts rapidly with the acetic acid, in accordance with the following equation:

and vinyl acetate, along with unreacted acetic acid and acetylene are continuously withdrawn from the reaction zone, while fresh acetic acid and catalyst, if necessary, are continuously introduced into the reaction zone. The pressure on the products withdrawn from the reaction zone may be released and the acetylene separated therefrom, and thereafter, the vinyl acetate separatedfrom the acetic acid by fractional distillation, vinyl acetate being obtained as a colorless liquid boiling at 73 C. in 85-95% yield.

Example 2 Acetylene at a pressure of 4 pounds per square isobutyl esters; also cyclohydroxy carboxylic 75 therewith and is then compressed to a pressure of .45 pounds per square inch and heated to a temperature of 145 C. It is then passegbinto a closed reaction vessel, filled with Valerie acid.

containing about 2.5% zinc acetate and mainv tained at a temperature of approximately 170 C.

. The acetylene reacts readily with the valeric acid to produce vinyl valerate in accordance with the' following equation:

- moor1+1icEcn-+cimco-o cH=cm 1)urlng the reaction, acetylene, diluted with cy- --clohexane, is continuously removed from the reaction zone and fresh diluted acetylene intro- J duced thereinto. When the acetylene is no longer Example 3 Acetylene at 4 pounds per square inch is passed through a bath of cyclohexane maintained at- 79 0., and becomes saturated therewith and is-then --compressed to 45 pounds per square inch and heated to 145 C. It is then introduced into a closed reaction vessel charged with 200 pounds oleic acid, 40 pounds cyclohexane and 14 pounds "of zinc acetate from which oxygen has been removed by flushing with nitrogen and the nitrogen removed by evacuation. The mixture in the reaction vessel is maintained at 160 C. The acetylene readily reacts with the oleic acid to formvlnyl oleate in accordance with the following equation:

"During the reaction, unreacted acetylene and -cyclohexane may be continuously withdrawn from the reaction zone while fresh diluted acetylene is continuously introduced thereinto. When the theoretical amount of acetylene has been absorbed, the reaction mixture isthen allowed to" cool, then filtered to remove zinc acetate and the filtrate fractionally distilled. After separating -'oif the cyclohexane, vinyl oleate boiling at 173- 175 C. at 2 mm. pressure is obtained in 90-95% y eld. 1 We claim: 1. In a process of producing vinyl esters wherein acetylene is introduced into a reaction zone and reacted therein with an organic carboxylic acid maintained in said reaction zone under elevated conditions of temperature and pressure at which the acetylene is normally explosive, the method of eliminating the danger of acety- --lene explosion which comprises contacting the acetylene which is supplied to said reaction zone while it is under non-explosive conditions of temperature and pressure with a volatile normally liquid organic compound selected from the group consisting of volatile organic liquid diluents which are inert in said reaction and volatile organic acids employed in said reaction, said contacting being eflected while said volatile normally liquid 7 organic compound is in liquid phase and is main 'atained at such a predetermined temperature that the-acetylene on contact therewith becomes sat- 1 -s,.4va,oec

urated with the vapors c! said volatile normally liquid organic compound in such an amount as to form a mixture of acetylene and such vapors in such predetermined ratio that said mixture is non-explosive at said normally explosive reaction conditions, adjusting the pressure and temperature of the thus formed mixture to said normally explosive reaction conditions, introducing the at which said vapors will condense and therein thus obtained mixture into said reaction zone while maintaining it at a temperature above that eflecting the desired reaction between said acetylene and said organic carboxylic acid to produce a vinyl ester and recovering the same. 15v

2. In a process of producing vinyl esters or volatile organic carboxylic acids wherein-acetylene is introduced into a reaction zone and reacted therein with a volatile organic carboxylicv acid maintained therein under elevated conditions of temperature and pressure at which the acetylene is normally explosive, the method of eliminating the danger of acetylene explosion which com-- prises contacting the acetylene which is supplied to said reaction zone while it is under non-explosive conditions of temperature and pressure with a body of said volatile organic carboxylic acid in liquid phase and maintained at such a predetermined temperature that the acetylene on contact therewith becomes saturated with the vapors of said volatile organic carboxylic acid in such an amount as to form a mixture of acetylene and such vapors in such predetermined ratio that said mixture is non-explosive at said normally explosive reaction conditions, adjusting the pressure and temperature of the thus formed mixture to said normally explosive reaction conditions, introducing the thus obtained mixture into said reaction zone while maintaining it at a temperature above that-at which said vapors will condense, eifecting the desired reaction between said acetylene and said volatile organic carboxylic acid in said reaction zone to produce a vinyl ester and recovering the same.

3. A process as defined in claim 2, wherein the volatile organic carboiwlic acid specified is acetic acid and the vinyl ester produced is vinyl acetate.

4. In a process of producing a vinyl ester wherein acetylene is introduced into a reaction zone and reacted therein with an organic carboxylic acid under elevated conditions of temperature and pressure at which the acetylene is normally explosive, the method of eliminating the danger of acetylene explosion which comprises contacting the acetylene supplied to said reaction zone while it is under non-explosive conditions of temperature and pressure with a non-explosive volatile normally liquid organic compound which is inert to both the acetylene and the organic acid under the conditions of reaction, while said volatile normally liquid organic compound is in liquid phase and is maintained at such a predetermined temperature that the acetylene on contact therewith becomes saturated with the vapors of said normally liquid organic compound in such an amount as to form a mixture of acetylene and such vapors in ,such predetermined ratio that said mixture is non-explosive at said normally explo-.

dense and therein efiecting the desired reaction between the acetylene and said organic carboxylic 4 7 acid to produce a. vinyl ester and recoverinl the REFERENCES CITED same.

5. 'A procees as defined in claim 4, wherein the y: figw fi m organic ccrboxylic acid specified is Valerie acid and the vinyl ester progxced 11s vinzl 1mg. h 5 UNITED STATES PATENTS 6.Aprocessasdefln incaim .were te be "m organic carboxylic acid specified is oleic acid and 2 3 g at a] i? 1928 vinyl Pmduced vinyl 1 1,786,647 mum. et '11. L Dec: 30, 1930 gg fi g'fi 1,822,525 Herman et a1. Sept. e, 1931 10 2,066,075 Reppe Dec. 29, 1938 m m' 2,176,958 Dreyfus on. 24, 1939 

